Heat 2 tablespoons olive oil in a large pot over medium-high heat. Add the celery, carrots, onion, 1/2 teaspoon salt and a dash of black pepper. Cook, stirring occasionally, until the vegetables are tender. About 7 minutes. Half way through the cooking time, add in the minced garlic.

Add 3 cups water, 3 cups vegetable stock, chickpeas, tomatoes, 2 teaspoons cumin, 1 teaspoon coriander and 1/2 teaspoon salt. Bring to a simmer and cook, stirring occasionally and slightly mashing the chickpeas with the back of a spoon, until the soup thickens slightly, about 20 minutes. Season with salt and pepper, to taste.

Meanwhile, slick the pitas into thin wedges. Toss with the remaining 2 tablespoons olive oil, 1 teaspoon cumin and 1/2 teaspoon coriander and 1/2 teaspoon salt. Spread in a single layer on a baking sheet. Bake until crisp, about 8-10 minutes.

Stir the lemon juice into the soup just before serving. Top with cilantro and the toasted pita chips.